Antibody or antibody fragments specific for a protein of the TGF-β family

ABSTRACT

The invention provides antibody and antibody fragments which specifically bind to novel members of the TGF-β family of proteins. The TFG-β family comprises proteins which function as growth and/or differentiation factors and which are useful in medical applications. Accordingly, the invention also applies to the production of said antibodies or antibody fragments and a diagnostic method for detecting said proteins of the TGF-β family.

This application is a div of 08/289,222 filed Aug. 12, 1994, now U.S. Pat. No. 6,120,760

The present invention relates to DNA sequences encoding novel growth/differentiation factors of the TGF-β family. In particular, it relates to novel DNA sequences encoding TGF-β-like proteins, to the isolation of said DNA sequences, to expression plasmids containing said DNA, to microorganisms transformed by said expression plasmid, to the production of said protein by culturing said transformant, and to pharmaceutical compositions containing said protein. The TGF-βfamily of growth factors comprising BMP, TGF, and Inhibin related proteins (Roberts and Sporn, Handbook of Experimental Pharmacology 95 (1990), 419-472) is of particular relevance in a wide range of medical treatments and applications. These factors are useful in processes relating to wound healing and tissue repair. Furthermore, several members of the TGF-βfamily are tissue inductive, especially osteo-inductive, and consequently play a crucial role in inducing cartilage and bone development.

Wozney, Progress in Growth Factor Research 1 (1989). 267-280 and Vale et al., Handbook of Experimental Pharmacology 95 (1990), 211-248 describe different growth factors such as those relating to the BMP (bone morphogenetic proteins) and the Inhibin group. The members of these groups share significant structural similarity. The precursor of the protein is composed of an aminoterminal signal sequence, a propeptide and a carboxyterminal sequence of about 110 amino acids, which is subsequently cleaved from the precursor and represents the mature protein. Furthermore, their members are defined by virtue of amino acid sequence homology. The mature protein contains the most conserved sequences, especially seven cysteine residues which are conserved among the family members. The TGF-β-like proteins are multifunctional, hormonally active growth factors. They also share related biological activities such as chemotactic attraction of cells, promoting cell differentiation and their tissue-inducing capacity, such as cartilage- and bone-inducing capacity. U.S. Pat. No. 5,013,649 discloses DNA sequences encoding osteo-inductive proteins termed BMP-2 proteins (bone morphogenetic protein), and U.S. Pat. applications Ser. Nos. 179,101 and 179,197 disclose the BMP proteins BMP-1 and BMP-3. Furthermore, many cell types are able to synthesize TGF-β-like proteins and virtually all cells possess TGF-β receptors.

Taken together, these proteins show differences in their structure, leading to considerable variation in their detailed biological function. Furthermore, they are found in a wide variety of different tissues and developmental stages. Consequently, they might possess differences concerning their function in detail, for instance the required cellular physiological environment, their lifespan, their targets, their requirement for accessory factors, and their resistance to degradation. Thus, although numerous proteins exhibiting tissue-inductive, especially osteo-inductive potential are described, their natural role in the organism and, more importantly, their medical relevance must still be elucidated in detail. The occurrence of still-unknown members of the TGF-β family relevant for osteogenesis or differentiation/induction of other tissues is strongly suspected. However, a major problem in the isolation of these new TGF-β-like proteins is that their functions cannot yet be described precisely enough for the design of a discriminative bioassay. On the other hand, the expected nucleotide sequence homology to known members of the family would be too low to allow for screening by classical nucleic acid hybridization techniques. Nevertheless, the further isolation and characterization of new TGF-β-like proteins is urgently needed in order to get hold of the whole set of induction and differentiation proteins meeting all desired medical requirements. These factors might find useful medical applications in defect healing and treatments of degenerative disorders of bone and/or other tissues like, for example, kidney and liver.

Thus, the technical problem underlying the present invention essentially is to provide DNA sequences coding for new members of the TGF-β protein family having mitogenic and/or differentiation-inductive, e.g. osteo-inductive potential.

The solution to the above technical problem is achieved by providing the embodiments characterized in claims 1 to 17. Other features and advantages of the invention will be apparent from the description of the preferred embodiments and the drawings. The sequence listings and drawings will now briefly be described.

SEQ ID NO. 1 shows the nucleotide sequence of MP-52, i.e. the embryo derived sequence corresponding to the mature peptide and most of the sequence coding for the propeptide of MP-52.

Some of the propeptide sequence at the 5′-end of MP-52 has not been characterized so far.

SEQ ID NO. 2 shows the nucleotide sequence of MP-121, i.e. the liver derived sequence corresponding to the mature peptide, the sequence coding for the propeptide of MP-121, and sequences 5′ and 3′ to the coding region.

The start codon begins with nucleotide 128 of SEQ ID NO.2. The sequence coding for the mature MP121 polypeptide begins with nucleotide 836 of SEQ ID NO. 2. The stop codon begins with nucleotide 1184 of SEQ ID NO. 2. The sequence coding for the precursor protein has a length of 1056 bp. The sequence coding for the propeptide has a length of 708 bp and the sequence coding for the mature peptide has a length of 348 bp.

SEQ ID NO. 3 shows the amino acid sequence of MP-52 as deduced from SEQ ID NO. 1.

SEQ ID NO. 4 shows the amino acid sequence of MP-121 as deduced from sequence SEQ ID NO.2. The sequence of the mature polypeptide begins with amino acid 237 of SEQ ID NO. 4. The precursor protein has a length of 352 amino acids. The propeptide and the mature peptide have a length of 236 and 116 amino acids, respectively.

SEQ ID NO. 5 shows a part of the nucleotide sequence of the liver derived sequence of MP-121.

SEQ ID NO. 6 shows a part of the nucleotide sequence of the embryo derived sequence of MP-52.

The shorter DNA-sequences SEQ ID NO. 5 and 6 can be useful for example for isolation of further members of the TGF-β-protein family.

FIG. 1 shows an alignment of the amino acid sequences of MP-52 and MP-121 starting from the first of the seven conserved cysteines with some related proteins. 1 a shows the alignment of MP-52 with some members of the BMP protein family (SEQ ID NOS: 22-27); 1 b shows the alignment of MP-121 with some members of the Inhibin protein family (SEQ ID NOS: 28-31). * indicates that the amino acid is the same in all proteins compared; + indicates that the amino acid is the same in at least one of the proteins compared with MP-52 (FIG. 1 a) or MP-121 (FIG. 1 b).

FIG. 2 shows the nucleotide sequences of the oligo-nucleotide primer as used in the present invention and an alignment of these sequences with known members of the TGF-β family. M means A or C; S means C or G; R means A or G; and K means G or T: 2 a depicts the sequence of the primer OD (SEQ ID NOS: 32-42); 2 b shows the sequence of the primer OID (SEQ ID NOS: 43-53).

The present invention relates to novel TGF-β-like proteins and provides DNA sequences contained in the corresponding genes. Such sequences include nucleotide sequences comprising the sequence

ATGAACTCCATGGACCCCGAGTCCACA (SEQ ID NO: 7) and

CTTCTCAAGGCCAACACAGCTGCAGGCACC (SEQ ID NO: 8)

and in particular sequences as illustrated in SEQ ID NOS: 1 and 2, allelic derivatives of said sequences and DNA sequences degenerated as a result of the genetic code for said sequences. They also include DNA sequences hybridizing under stringent conditions with the DNA sequences mentioned above and containing the following amino acid sequences:

Met-Asn-Ser-Met-Asp-Pro-Glu-Ser-Thr (SEQ ID NO: 9) or

Leu-Leu-Lys-Ala-Asn-Thr-Ala-Ala-Gly-Thr (SEQ ID NO: 10).

Although said allelic, degenerate and hybridizing sequences may have structural divergencies due to naturally occurring mutations, such as small deletions or substitutions, they will usually still exhibit essentially the same useful properties, allowing their use in basically the same medical applications.

According to the present invention, the term “hybridization”means conventional hybridization conditions, preferably conditions with a salt concentration of 6×SSC at 62° to 66° C. followed by a one-hour wash with 0.6×SSC, 0.1% SDS at 62° to 66° C. The term “hybridization” preferably refers to stringent hybridization conditions with a salt concentration of 4×SSC at 62°-66° C. followed by a one-hour wash with 0.1×SSC, 0.1% SDS at 62°-66° C.

Important biological activities of the encoded proteins, preferably MP-52, comprise a mitogenic and osteo-inductive potential and can be determined in assays according to Seyedin et al., PNAS 82 (1985), 2267-2271 or Sampath and Reddi, PNAS 78 (1981), 7599-7603.

The biological properties of the proteins according to the invention, preferably MP-121, may be determined, e.g., by means of the assays according to Wrana et al. (Cell 71, 1003-1014 (1992)), Ling et al. (Proc. Natl. Acad. of Science, 82, 7217-7221 (1985)), Takuwa et al. (Am. J. Physiol., 257, E797-E803 (1989)), Fann and Patterson (Proc. Natl. Acad. of Science, 91, 43-47 (1994)), Broxmeyer et al. (Proc. Natl. Acad. of Science, 85, 9052-9056 (1988)), Green et al. (Cell, 71, 731-739 (1992)), Partridge et al. (Endocrinology, 108, 213-219 (1981)) or Roberts et al. (PNAS 78, 5339-5343 (1981)).

Preferred embodiments of the present invention are DNA sequences as defined above and obtainable from vertebrates, preferably mammals such as pig or cow and from rodents such as rat or mouse, and in particular from primates such as humans.

Particularly preferred embodiments of the present invention are the DNA sequences termed MP-52 and MP-121 which are shown in SEQ ID Nos. 1 and 2. The corresponding transcripts of MP-52 were obtained from embryogenic tissue and code for a protein showing considerable amino acid homology to the mature part of the BMP-like proteins (see FIG. 1 a). The protein sequences of BMP2 (=BMP2A) and BMP4 (=BMP2B) are described in Wozney et al., Science Vol 242, 1528-1534 (1988). The respective sequences of BMP5, BMP6 and BMP7 are described in Celeste et al., Proc. Natl. Acad. Sci. USA Vol 87, 9843-9847 (1990). Some typical sequence homologies, which are specific to known BMP-sequences only, were also found in the propeptide part of MP-52, whereas other parts of the precursor part of MP-52 show marked differences to BMP-precursors. The mRNA of MP-121 was detected in liver tissue, and its correspondig amino acid sequence shows homology to the amino acid sequences of the Inhibin protein chains (see FIG. 1 b). cDNA sequences encoding TGF-β-like proteins have not yet been isolated from liver tissue, probably due to a low abundance of TGF-β specific transcripts in this tissue. In embryogenic tissue, however, sequences encoding known TGF-β-like proteins can be found in relative abundance. The inventors have recently detected the presence of a collection of TGF-β-like proteins in liver as well. The high background level of clones related to known factors of this group presents the main difficulty in establishing novel TGF-β-related sequences from these and probably other tissues. In the present invention, the cloning was carried out according to the method described below. Once the DNA sequence has been cloned, the preparation of host cells capable of producing the TGF-β-like proteins and the production of said proteins can be easily accomplished using known recombinant DNA techniques comprising constructing the expression plasmids encoding said protein and transforming a host cell with said expression plasmid, cultivating the transformant in a suitable culture medium, and recovering the product having TGF-β-like activity.

Thus, the invention also relates to recombinant molecules comprising DNA sequences as described above, optionally linked to an expression control sequence. Such vectors may be useful in the production of TGF-β-like proteins in stably or transiently transformed cells. Several animal, plant, fungal and bacterial systems may be employed for the transformation and subsequent cultivation process. Preferably, expression vectors which can be used in the invention contain sequences necessary for the replication in the host cell and are autonomously replicable. It is also preferable to use vectors containing selectable marker genes which can be easily selected for transformed cells. The necessary operation is well-known to those skilled in the art.

It is another object of the invention to provide a host cell transformed by an expression plasmid of the invention and capable of producing a protein of the TGF-β family. Examples of suitable host cells include various eukaryotic and prokaryotic cells, such as E. coli, insect cells, plant cells, mammalian cells, and fungi such as yeast.

Another object of the present invention is to provide a protein of the TGF-β family encoded by the DNA sequences described above and displaying biological features such as tissue-inductive, in particular osteo-inductive and/or mitogenic capacities possibly relevant to therapeutical treatments. The above-mentioned features of the protein might vary depending upon the formation of homodimers or heterodimers. Such structures may prove useful in clinical applications as well. The amino acid sequence of the especially preferred proteins of the TGF-β-family (MP-52 and MP-121) are shown in SEQ ID NO. 3 and SEQ ID NO. 4.

It is a further aspect of the invention to provide a process for the production of TGF-β-like proteins. Such a process comprises cultivating a host cell being transformed with a DNA sequence of the present invention in a suitable culture medium and purifying the TGF-β-like protein produced. Thus, this process will allow the production of a sufficient amount of the desired protein for use in medical treatments or in applications using cell culture techniques requiring growth factors for their performance. The host cell is obtainable from bacteria such as Bacillus or Escherichia coli, from fungi such as yeast, from plants such as tobacco, potato, or Arabidopsis, and from animals, in particular vertebrate cell lines such as the Mo-, COS- or CHO cell line.

Yet another aspect of the present invention is to provide a particularly sensitive process for the isolation of DNA sequences corresponding to low abundance mRNAs in the tissues of interest. The process of the invention comprises the combination of four different steps. First, the mRNA has to be isolated and used in an amplification reaction using olignucleotide primers. The sequence of the oligonucleotide primers contains degenerated DNA sequences derived from the amino acid sequence of proteins related to the gene of interest. This step may lead to the amplification of already known members of the gene family of interest, and these undesired sequences would therefore have to be eliminated. This object is achieved by using restriction endonucleases which are known to digest the already-analyzed members of the gene family. After treatment of the amplified DNA population with said restriction endonucleases, the remaining desired DNA sequences are isolated by gel electrophoresis and reamplified in a third step by an amplification reaction, and in a fourth step they are cloned into suitable vectors for sequencing. To increase the sensitivity and efficiency, steps two and three are repeatedly performed, at least two times in one embodiment of this process.

In a preferred embodiment, the isolation process described above is used for the isolation of DNA sequences from liver tissue. In a particularly preferred embodiment of the above-described process, one primer used for the PCR experiment is homologous to the polyA tail of the mRNA, whereas the second primer contains a gene-specific sequence. The techniques employed in carrying out the different steps of this process (such as amplification reactions or sequencing techniques) are known to the person skilled in the art and described, for instance, in Sambrook et al., 1989, “Molecular Cloning: A laboratory manual”, Cold Spring Harbor Laboratory Press.

It is another object of the present invention to provide pharmaceutical compositions containing a therapeutically-effective amount of a protein of the TGF-β family of the present invention. Optionally, such a composition comprises a pharmaceutically acceptable carrier. Such a therapeutic composition can be used in wound healing and tissue repair as well as in the healing of bone, cartilage, or tooth defects, either individually or in conjunction with suitable carriers, and possibly with other related proteins or growth factors. Thus, a therapeutic composition of the invention may include, but is not limited to, the MP-52 encoded protein in conjunction with the MP-121 encoded protein, and optionally with other known biologically-active substances such as EGF (epidermal growth factor) or PDGF (platelet derived growth factor). Another possible clinical application of a TGF-β-like protein is the use as a suppressor of the immuno response, which would prevent rejection of organ transplants. The pharmaceutical composition comprising the proteins of the invention can also be used prophylactically, or can be employed in cosmetic plastic surgery. Furthermore, the application of the composition is not limited to humans but can include animals, in particular domestic animals, as well. Possible applications of the pharmaceutical composition according to the invention include furthermore treatment or prevention of connective tissue, skin, mucous membrane, endothelial, epithelial, neuronal or renal defects, use in the case of dental implants, use as a morphogenic factor used for inducing liver tissue growth, induction of the proliferation of precursor cells or bone marrow cells, for maintaining a differentiated state and the treatment of impaired fertility or for contraception.

Finally, another object of the present invention is an antibody or antibody fragment, which is capable of specifically binding to the proteins of the present invention. Methods to raise such specific antibody are general knowledge. Preferably such an antibody is a monoclonal antibody. Such antibodies or antibody fragments might be useful for diagnostic methods.

The following examples illustrate in detail the invention disclosed, but should not be construed as limiting the invention.

Example 1 Isolation of MP-121

-   1.1 Total RNA was isolated from human liver tissue     (40-year-old-male) by the method of Chirgwin et al., Biochemistry 18     (1979), 5294-5299. Poly A⁺ RNA was separated from total RNA by oligo     (dT) chromatography according to the instructions of the     manufacturer (Stratagene Poly (A) Quick columns). -   1.2 For the reverse transcription reaction, poly A⁺ RNA (1-2.5 μg)     derived from liver tissue was heated for 5 minutes to 65° C. and     cooled rapidly on ice. The reverse transcription reagents containing     27 U RNA guard (Pharmacia), 2.5 μg oligo d(T)₁₂₋₁₈ (Pharmacia) 5×     buffer (250 mM Tris/HCl pH 8.5; 50 mM MgCl₂; 50 mM DTT; 5 mM each     dNTP; 600 mM KCl ) and 20 units avian myeloblastosis virus reverse     transcriptase (AMV, Boehringer Mannheim) per μg poly (A⁺) RNA were     added. The reaction mixture (25 μl ) was incubated for 2 hours at     42° C. The liver cDNA pool was stored at −20° C. -   1.3 The deoxynucleotide primers OD and OID (FIG. 2) designed to     prime the amplification reaction were generated on an automated     DNA-synthesizer (Biosearch). Purification was done by denaturating     polyacrylamide gel electrophoresis and isolation of the main band     from the gel by isotachophoresis. The oligonucleotides were designed     by aligning the nucleic acid sequences of some known members of the     TGF-β family and selecting regions of the highest conservation. An     alignment of this region is shown in FIG. 2. In order to facilitate     cloning, both oligonucleotides contained EcoR I restriction sites     and OD additionally contained an Nco I restriction site at its 5′     terminus. -   1.4 In the polymerase chain reaction, a liver-derived cDNA pool was     used as a template in a 50 μl reaction mixture. The amplification     was performed in 1×PCR-buffer (16.6 mM (NH₄)₂ SO₄; 67 mM Tris/HCl pH     8.8; 2 mM MgCl₂; 6.7 μM EDTA; 10 mM β-mercaptoethanol; 170 μg/ml BSA     (Gibco)), 200 μM each dNTP (Pharmacia), 30 pmol each oligonucleotide     (OD and OID) and 1.5 units Taq polymerase (AmpliTaq, Perkin Elmer     Cetus). The PCR reaction contained cDNA corresponding to 30 ng of     poly (A⁺) RNA as staring material. The reaction mixture was     overlayed by paraffine and 40 cycles (cycle 1: 80s 93° C./40s 52°     C./40s 72° C.; cycles 2-9: 60s 93° C./40s 52° C./40s 72° C.; cycles     10-29: 60s 93° C./40s 52° C./60s 72° C.; cycles 30-31: 60s 93°     C./40s 52° C./90s 72° C.; cycle 40: 60s 93° C./40s 52° C./420s 72°     C.) of the PCR were performed. Six PCR-reaction mixtures were     pooled, purified by subsequent extractions with equal volumes of     phenol, phenol/chloroform (1:1 (v/v)) and chloroform/isoamylalcohol     (24:1 (v/v)) and concentrated by ethanol precipitation. -   1.5 One half of the obtained PCR pool was sufficient for digestion     with the restriction enzymes Sph I (Pharmacia) and AlwN I (Biolabs).     The second half was digested in a series of reactions by the     restriction enzymes Ava I (BRL), AlwN I (Biolabs) and Tfi I     (Biolabs). The restriction endonuclease digestions were performed in     100 μl at 37° C. (except Tfi I at 65° C.) using 8 units of each     enzyme in a 2- to 12-hour reaction in a buffer recommended by the     manufacturer. -   1.6 Each DNA sample was fractioned by electrophoresis using a 4%     agarose gel (3% FMC Nusieve agarose, Biozym and 1% agarose, BRL) in     Tris borate buffer (89 mM Trisbase, 89 mM boric acid, 2 mM EDTA, pH     8). After ethidiumbromide staining uncleaved amplification products     (about 200 bp; size marker was run in parallel) were excised from     the gel and isolated by phenol extraction: an equal volume of     phenols was added to the excised agarose, which was minced to small     pieces, frozen for 10 minutes, vortexed and centrifuged. The aqueous     phase was collected, the interphase reextracted by the same volume     TE-buffer, centrifuged and both aqueous phases were combined. DNA     was further purified twice by phenol/chloroform and once by     chloroform/isoamylalcohol extraction. -   1.7 After ethanol precipitation, one fourth or one fifth of the     isolated DNA was reamplified using the same 52° C./60s 72° C.; cycle     13: 60s 93° C./40s 52° C./420s 72° C.). The reamplification products     were purified, restricted with the same enzymes as above and the     uncleaved products were isolated from agarose gels as mentioned     above for the amplification products. The reamplification followed     by restriction and gel isolation was repeated once. -   1.8 After the last isolation from the gel, the amplification     products were digested by 4 units EcoR I (Pharmacia) for 2 hours at     37° C. using the buffer recommended by the manufacturer. One fourth     of the restriction mixture was ligated to the vector pBluescriptIl     SK+ (Stratagene) which was digested likewise by EcoR I. After     ligation, 24 clones from each enzyme combination were further     analyzed by sequence analysis. The sample restricted by AlwN I and     Sph I contained no new sequences, only BMP6 and Inhibin βA     sequences. 19 identical new sequences, which were named MP-121, were     found by the Ava I, AlwN I and Tfi I restricted samples. The MP-121     containing plasmids were called pSK MP-121 (OD/OID). One sequence     differed from this mainly-found sequence by two nucleotide     exchanges. Ligation reaction and transformation in E. coli HB101     were performed as described in Sambrook et al., Molecular cloning: A     laboratory manual (1989). Transformants were selected by Ampicillin     resistance and the plasmid DNAs were isolated according to standard     protocols (Sambrook et al. (1989)). Analysis was done by sequencing     the double-stranded plasmids by “dideoxyribonucleotide chain     termination sequencing” with the sequencing kit “Sequenase Version     2.0 ” (United States Biochemical Corporation).

The clone was completed to the 3′ end of the cDNA by a method described in detail by Frohman (Amplifications, published by Perkin-Elmer Corporation, issue 5 (1990), pp 11-15). The same liver mRNA which was used for the isolation of the first fragment of MP-121 was reverse transcribed using a primer consisting of oligo dT (16 residues) linked to an adaptor primer (AGAATTCGCATGCCATGGTCGACGAAGC(T)₁₆ (SEQ ID NO: 11)). Amplification was performed using the adaptor primer (AGAATTCGCATGCCATGGTCGACG (SEQ ID NO: 12)) and an internal primer (GGCTACGCCATGAACTTCTGCATA (SEQ ID NO: 13)) of the MP-121 sequence. The amplification products were reamplified using a nested internal primer (ACATAGCAGGCATGCCTGGTATTG (SEQ ID NO: 14)) of the MP-121 sequence and the adaptor primer. The reamplification products were cloned after restriction with Sph I in the likewise restricted vector pT7/T3 U19 (Pharmacia) and sequenced with the sequencing kit “Sequenase Version 2.0” (United States Biochemical Corporation). Clones were characterized by their sequence overlap to the 3′ end of the known MP-121 sequence.

One clone, called p121Lt 3′ MP13, was used to isolate a NcoI (blunt ended with T4 polymerase)/SphI fragment. This fragment was ligated into a pSK MP-121 (OD/OID) vector, where the OD primer sequence was located close to the T7 primer sequence of the pSK+ multiple cloning site, opened with SphI/SmaI. The resulting plasmid was called pMP121DFus6. It contains MP-121 specific sequence information starting from position 922 and ending with position 1360 of SEQ ID NO. 2.

-   1.9 Using a DdeI fragment of pMP-121DFus6 as a probe, ranging from     nucleotide 931 to nucleotide 1304 of SEQ ID NO. 2, a human liver     cDNA library (Clontech, # HL3006b, Lot 36223) was screened by a     common method described in detail by Ausubel et al. (Current     Protocols in Molecular Biology, published by Greene Publishing     Associates and Wiley-Interscience (1989)). From 8.1×10⁵ phages, 24     mixed clones were isolated and re-screened using the DdeI fragment.     10 clones were confirmed and the EcoRI fragments subcloned into     Bluescript SK (Stratagene, #212206). EcoRI restriction analysis     showed that one clone (SK121 L9.1, deposited by the DSM (#9177) has     an insert of about 2.3 kb. This clone contains the complete reading     frame of the MP121 gene and further information to the 5′ and 3′ end     in addition to the sequence isolated from mRNA by the described     amplification methods. The complete sequence of the EcoRI insert of     SK121 L9.1 is shown in SEQ ID NO.2. The reading frame of the MP-121     gene could be confirmed by sequencing of another clone (SK121     L11.1), having the identical reading frame sequence as SK121 L9.1.     The beginning of the start codon of the MP-121 sequence of SK121     L9.1 could be determined at position 128 of SEQ ID NO.2, since there     are three stop codons in-frame in front of the start codon at     positions 62, 77 and 92. The start site of the mature MP-121 is at     position 836 of SEQ ID NO.2 in sequence analogy to other members of     the TGF-β-family, corresponding to amino acid 237 in SEQ ID NO.4.     The stop codon is at position 1184 of SEQ ID NO.2.

Plasmid SK121 L9.1 was deposited under number 9177 at DSM (Deutsche Sammlung von Mikroorganismen und Zellkulturen), Mascheroder Weg 1b, Braunschweig, on 26.04.94).

Example 2 Isolation of MP-52

A further cDNA sequence, MP-52, was isolated according to the above described method (Example 1) by using RNA from human embryo (8-9 weeks old) tissue. The PCR reaction contained cDNA corresponding to 20 ng of poly (A+)RNA as starting material. The reamplification step was repeated twice for both enzyme combinations. After ligation, 24 clones from each enzyme combination were further analyzed by sequence analysis. The sample resticted by AlwN I and Sph I yielded a new sequence which was named MP-52. The other clones comprised mainly BMP6 and one BMP7 sequence. The sample restricted by Ava I, AlwN I and Tfi I contained no new sequences, but consisted mainly of BMP7 and a few Inhibin βA sequences.

The clone was completed to the 3′ end according to the above described method (Example 1). The same embryo mRNA, which was used for the isolation of the first fragment of MP-52, was reverse transcribed as in Example 1. Amplification was performed using the adaptor primer (AGAATTCGCATGCCATGGTCGACG (SEQ ID NO: 12)) and an internal primer (CTTGAGTACGAGGCTTTCCACTG (SEQ ID NO: 15)) of the MP-52 sequence. The amplification products were reamplified using a nested adaptor primer (ATTCGCATGCCATGGTCGACGAAG (SEQ ID NO 16)) and a nested internal primer (GGAGCCCACGAATCATGCAGTCA (SEQ ID NO: 17)) of the MP-52 sequence . The reamplification products were cloned after restriction with Nco I in a likewise restricted vector (pUC 19 (Pharmacia #27-4951-01) with an altered multiple cloning site containing a unique Nco I restriction site) and sequenced. Clones were characterized by their sequence overlap to the 3′ end of the known MP-52 sequence. Some of these clones contain the last 143 baspairs of the 3′ end of the sequence shown in SEQ ID NO: 1 and the 0.56 kb 3′ non-translated region (sequence not shown). One of these was used as a probe to screen a human genomic library (Stratagene #946203) by a common method described in detail by Ausubel et al. (Current Protocols in Molecular Biology, published by Greene publishing Associates and Wiley-lnterscience (1989)). From 8×10⁵ λ phages one phage (λ 2.7.4) which was proved to contain an insert of about 20 kb, was isolated and deposited by the DSM (#7387). This clone contains in addition to the sequence isolated from mRNA by the described amplification methods sequence information further to the 5′ end. For sequence analysis a Hind III fragment of about 7.5 kb was subcloned in a likewise restricted vector (Bluescript SK, Stratagene #212206). This plasmid, called SKL 52 (H3) MP12, was also deposited by the DSM (#7353). Sequence information derived from this clone is shown in SEQ ID NO: 1. At nucleotide No. 1050, the determined cDNA and the respective genomic sequence differ by one basepair (cDNA:G, genomic DNA:A). We assume the genomic sequence to be correct, as it was confirmed also by sequencing of the amplified genomic DNA from embryonic tissue which had been used for the mRNA preparation. The genomic DNA contains an intron of about 2 kb between basepairs 332 and 333 of SEQ ID NO: 1. The sequence of the intron is not shown. The correct exon/exon junction was confirmed by sequencing an amplification product derived from cDNA which comprises this region. This sequencing information was obtained by the help of a slightly modified method described in detail by Frohman (Amplifications, published by Perkin-Elmer Corporation, issue 5 (1990), pp 11-15). The same embryo RNA which was used for the isolation of the 3′ end of MP-52 was reverse transcribed using an internal primer of the MP-52 sequence oriented in the 5′ direction (ACAGCAGGTGGGTGGTGTGGACT (SEQ ID NO: 18)). A polyA tail was appended to the 5′ end of the first strand cDNA by using terminal transferase. A two step amplification was performed first by application of a primer consisting of oligo dT and an adaptor primer (AGAATTCGCATGCCATGGTCGACGAAGC (T₆) (SEQ ID NO: 11)) and secondly an adaptor primer (AGAATTCGCATGCCATGGTCGACG (SEQ ID NO. 12)) and an internal primer (CCAGCAGCCCATCCTTCTCC (SEQ ID NO: 19)) of the MP-52 sequence. The amplification products were reamplified using the same adaptor primer and a nested internal primer (TCCAGGGCACTAATGTCAAACACG (SEQ ID NO: 20)) of the MP-52 sequence. Consecutively the reamplification products were again reamplified using a nested adaptor primer (ATTCGCATGCCATGGTCGACGAAG (SEQ

Plasmid SKL 52 (H3) MP12 was deposited under number 7353 at DSM (Deutsche Sammlung von Mikroorganismen und Zellkulturen), Mascheroder Weg 1b, 3300 Braunschweig, on 10.12.1992.

Phage λ 2.7.4. was deposited under number 7387 at DSM on 13.1.1993. 

1. An antibody or antibody fragment which specifically binds to a protein of the TGF-β family wherein said antibody or antibody fragment binds to a part of the protein encoded by nucleotide sequence selected from the following group: (a) the nucleotide sequence as shown in SEQ ID NO: 1, (b) a nucleotide sequence which is degenerate as a result of the genetic code to the nucleotide sequence of (a), and (c) fragments of (a) or (b) which encode a protein which has the cartilage or bone inducing activities of a mature protein encoded by the nucleotide sequence of SEQ ID NO:1.
 2. The antibody according to claim 1, wherein said antibody is a monoclonal antibody.
 3. An antibody or antibody fragment according to claim 1, which specifically binds to a protein of the TGF-β family wherein the protein to which the antibody or antibody fragment binds consists of an amino acid sequence according to SEQ ID NO:3.
 4. A kit for detecting a protein of the TGF-β family, comprising an antibody or antibody fragment which specifically binds to a protein of the TGF-βfamily, and a reaction buffer, wherein said antibody or antibody fragment binds to a part of the protein which is encoded by a nucleotide sequence selected from the following group: (a) the nucleotide sequence as shown in SEQ ID NO:1, (b) a nucleotide sequence which is degenerate to the nucleotide sequence of (a) as a result of the degeneracy of the genetic code, and (c) fragments of (a) or (b) which encode a protein which has the cartilage or bone inducing activities of a mature protein encoded by the nucleotide sequence of SEQ ID NO:1.
 5. An isolated antibody or antibody fragment which specifically binds to a protein of the TGF-β family wherein said antibody or antibody fragment binds to a fragment of SEQ ID NO:3, wherein said fragment of SEQ ID NO:3 comprises the amino acids shown in SEQ ID NO:22.
 6. An isolated antibody or antibody fragment which specifically binds to a protein of the TGF-β family wherein said antibody or antibody fragment binds to a part of the protein encoded by a nucleotide sequence selected from the following group: (a) the nucleotide sequence as shown in SEQ ID NO:1, (b) a nucleotide sequence which is degenerate to the nucleotide sequence of (a) as a result of the degeneracy of the genetic code, and (c) fragments of (a) or (b) which encode a protein which retains the cartilage or bone inducing activities of the protein encoded by the nucleotide sequence of SEQ ID NO:1.
 7. An isolated antibody or antibody fragment which specifically binds to a protein of the TGF-β family, wherein said protein is selected from the following group: (a) a protein encoded by DNA consisting of the nucleotide sequence as shown in SEQ ID NO:1, (b) a protein encoded by a DNA consisting of a fragment of the nucleotide sequence as shown in SEQ ID NO:1, wherein said fragment of SEQ ID NO:1 comprises the nucleotide sequence as shown in SEQ ID NO: 6, (c) a protein encoded by DNA consisting of a nucleotide sequence which is degenerate to the nucleotide sequence of (a) as a result of the degeneracy of the genetic code or (b), (d) a protein consisting of the amino acid sequence shown in SEQ ID NO:3, and (e) a protein consisting of a fragment of the amino acid sequence shown in SEQ ID NO: 3, wherein said fragment of SEQ ID NO:3 comprises the amino acid sequence shown in SEQ ID NO:22.
 8. The antibody according to claim 7, wherein said antibody is a monoclonal antibody. 